<!DOCTYPE html>
<html>
<body style="margin:0; background:white">
  <svg width="200" height="200" viewBox="0 0 200 200" xmlns="http://www.w3.org/2000/svg">
    <!-- luminanceToAlpha of red (alpha=0.2126) over white -> approx #C9C9C9 -->
    <rect x="10" y="10" width="180" height="180" fill="#C9C9C9"/>
  </svg>
</body>
</html>
